Today, many electronic devices include memory systems that are used to store information (data) utilized by the devices. For example, some digital audio players include memory systems that are used to store digitized audio that may be played by the player. Likewise, personal computers systems often employ memory systems to store software utilized by the personal computers.
In many electronic devices, memory systems often comprise a controller and one or more memory devices. The controller typically contains circuitry configured to control access to information stored in the memory devices. The controller's circuitry may contain logic configured to generate signals that are used to direct the memory devices to store and retrieve information.
The memory devices typically store the information in memory that is contained in the memory devices. The memory may be volatile or non-volatile. A memory device that contains volatile memory often loses the information when power is removed from the device. A memory device containing non-volatile memory retains the information even when the device is not powered.
In some memory systems, data and control signals are transferred between the controller and memory devices using a parallel bus. One example of a parallel bus approach is disclosed in “Open NAND Flash Interface Specification”, Revision 2.0, Feb. 27, 2008.
The parallel bus allows the data and control signals to be transferred in parallel between the controller and the memory devices. Many wires may be used to implement the bus and, depending on the layout of the memory system, the wires may extend for some length.
There are several disadvantages associated with transferring data and control signals in parallel between a controller and memory devices. One disadvantage relates to the complexity involved in implementing such systems. For example, the number of wires needed to implement the parallel bus may be quite significant and require the use of multi-layered printed circuit boards (PCBs). Another disadvantage relates to signal quality in the memory system. For example, parallel buses tend to be susceptible to crosstalk, signal skew, signal attenuation and noise, which may affect the quality of the signals carried by the wires. Another disadvantage associated with parallel bus designs relates to power consumption. Parallel bus designs tend to require a significant amount of power in order to drive the signals on the bus.
Accordingly, there is a need in the industry for improved memory devices and systems.